One of the difficulties to face when making corners, for example when building a house, is to set the sides perpendicular to each other. Although a room does not have to be perfectly square, the corners should be as wide as possible to 90 °; otherwise the tiles and the carpet will be "misaligned" in a very evident way with respect to one side of the room. The "3-4-5" method is very useful for small carpentry projects and ensures that all elements meet the schedule.
Steps
Method 1 of 1: Using the "3-4-5" Rule
Step 1. Understand the concept behind the method
If the sides of a triangle measure 3, 4, and 5 meters (or another unit of measurement), then the angle between the two shorter sides is 90 °. If you can "draw" this type of triangle using the corner of the room, then you are sure it is straight. This statement is based on the Pythagorean theorem, according to which, in a right triangle, A.2 + B2 = C2. Side C is the longest (hypotenuse), sides A and B are the two shortest, ie the "catheti".
The "3-4-5" rule is a very convenient method of measurement because it involves small and whole numbers. Here is the mathematical procedure to verify it: 32 + 42 = 9 + 16 = 25 = 52.
Step 2. Measure three units along one side of the corner
You can use the unit of your choice, such as meters, feet or centimeters. At this point, draw a mark to outline the segment you have detected.
You can also multiply each number by a constant factor and you will always get the same result. For example, you can draw a triangle with sides of 30-40-50 centimeters. If the room is large, you can consider a triangle of 6-8-10 meters or 9-12-15 meters
Step 3. Measure four units along the second side of the corner
It always uses the same unit to detect the segment on the second side which, hopefully, is perpendicular to the first. Make a mark here.
Step 4. Measure the distance between the two marks you made
If this "diagonal" is 5 units, then the angle is right.
- If the distance is less than 5 units, the angle is acute (less than 90 °) and you need to space the sides apart.
- If the distance is greater than 5 units, the angle is obtuse (greater than 90 °) and in this case you have to bring the sides together.
Advice
- This method is more accurate than using the carpenter's square, as this tool is too small to accurately measure very large spaces.
- The higher the unit of measurement, the more accurate the readings will be.
